Intermediate transfer member for a digital printing system

ABSTRACT

An intermediate transfer member (ITM) (210, 310, 320, 330, 400, 410, 420, 430, 500, 520, 540, 600, 700, 802) configured for receiving ink droplets to form an ink image thereon and for transferring the ink image to a target substrate (226), the TTM (210, 310, 320, 330, 400, 410, 420, 430, 500, 520, 540, 600, 700, 802) includes one or more layers (273, 277, 373, 379, 602, 604, 606, 608, 610, 704, 706, 708, 712) and one or more markers (33, 333, 335, 392, 408, 418, 428, 448, 458, 612, 710, 804, 806) integrated with at least one of the one or more layers (273, 277, 373, 379, 602, 604, 606, 608, 610, 704, 706, 708, 712) at one or more respective marking locations along the ITM (210, 310, 320, 330, 400, 410, 420, 430, 500, 520, 540, 600, 700).

This application is U.S. National Phase of PCT ApplicationPCT/IB2019/055288, which claims the benefit of U.S. Provisional PatentApplication 62/689,852, filed Jun. 26, 2018, and the benefit of U.S.Provisional Patent Application 62/715,822, filed Aug. 8, 2018, and thebenefit of U.S. Provisional Patent Application 62/748,569, filed Oct.22, 2018, and the benefit of U.S. Provisional Patent Application62/828,501, filed Apr. 3, 2019. The disclosures of these relatedapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to digital printing, andparticularly to methods and systems for controlling in the operation ofdigital printing systems.

BACKGROUND OF THE INVENTION

Various methods and devices for controlling processes in digitalprinting are known in the art.

For example, PCT Patent Application PCT/IB2013/051727 describes controlapparatus and methods for a printing system, for example, comprising anintermediate transfer member (ITM). Some embodiments relate toregulation of a velocity and/or tension and/or length of the ITM. Someembodiments relate to regulation of deposition of ink on the moving ITM.Some embodiments regulate to apparatus configured to alert a user of oneor more events related to operation of the ITM.

U.S. Pat. No. 5,889,534 describes a method of characterizing adrum-based digital print engine so that each of a plurality of inkdroplets propelled toward a common picture element location, or pixel,of a print media coupled to an exterior surface of a rotating drummember precisely reaches the same pixel location regardless of slightvariations in portions of the surface of the drum.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesa system that includes a flexible intermediate transfer member (ITM),one or more sensing assemblies, and a processor. The flexible ITMincluding a stack of multiple layers and having one or more markersengraved in at least one of the layers, at one or more respectivemarking locations along the ITM, the ITM is configured to receive inkdroplets from an ink supply system to form an ink image thereon, and totransfer the ink image to a target substrate. The one or more sensingassemblies are disposed at one or more respective predefined locationsrelative to the ITM, and are configured to produce signals indicative ofrespective positions of the markers. The processor is configured toreceive the signals, and, based on the signals, to control a depositionof the ink droplets on the ITM.

In some embodiments, at least one of the markers includes at least onecode selected from a list consisting of: a grid marker, a motionencoding code, a one-dimensional (1D) barcode, a two-dimensional (2D)barcode, and a three-dimensional (3D) barcode. In other embodiments, the2D barcode includes at least one of a quick response (QR) code and anAZTEC code. In yet other embodiments, at least one of the markers has ageometrical shape selected from a list consisting of a round shape, arectangular shape, a square shape, and a star shape.

In an embodiment, the system includes one or more light sourcesassociated respectively with at least one of the sensing assemblies,such that each light source is facing the respective sensing assembly orcoupled to the respective sensor, and each of the light sources isconfigured to illuminate the ITM. In another embodiment, the systemincludes a slit assembly, which is disposed between the ITM and thesensing assembly and having first and second slits, which are formed ata predefined distance from one another and are configured to pass,through the slit assembly, one or more light beams emitted from thelight source, when a given marker of the markers is aligned with thefirst slit, the sensing assembly is configured to produce a first signalindicative of a position of the given marker aligned with the firstslit, and when the given marker is aligned with the second slit, thesensing assembly is configured to produce a second signal indicative ofthe position of the given marker aligned with the second slit, and theprocessor is configured to detect, based on the first and secondsignals, a deformation of the ITM.

In some embodiments, the system includes a fiber assembly, which isdisposed between the slit assembly and the sensing assembly and havingmultiple optical fibers, which are configured to convey the light beamsthat pass through the slit assembly, to the sensing assembly. In otherembodiments, the light beams include a first light beam passing throughthe first slit and a second light beam passing through the second slit,and the system including a shield, which is disposed between the firstand second slits and is configured to isolate between the first andsecond light beams. In yet other embodiments, the markers include atleast the given marker and an adjacent marker located at an inter-markerdistance from the given marker, and the inter-marker distance is largerthan the predefined distance.

In an embodiment, when the ITM moves at a predefined speed relative tothe first and second slits, the processor is configured to detect thedethnnation of the ITM, based on the predefined speed and the first andsecond signals. In another embodiment, at least one of the light sourcesis configured to emit one of a visible light, an infrared (IR) light andan ultraviolet (UV) light, and at least one of the sensing assemblies isconfigured to sense the light emitted from the respective light sources.In yet another embodiment, at least one of the markers includes magneticmaterial, and at least one of the sensing assemblies is configured tosense a magnetic field produced between the magnetic material and thesensing assembly, and, based on the sensed magnetic field, to producethe signals.

In some embodiments, the system includes at least one station orassembly, the processor is configured, based on the signals, to controlan operation of the at least one station or assembly of the system. Inother embodiments, the at least one station or assembly is selected froma list consisting of (a) an image forming station, (b) an impressionstation, (c) an ITM guiding system, (d) one or more drying assemblies,(e) an ITM treatment station, and (f) an image quality control station.In yet other embodiments, the image forming station includes at least aprint bar including one or more print heads, and the image formingstation is coupled to the ink supply system and configured to receivethe ink therefrom, and to apply the ink droplets to the ITM using theprint heads.

In an embodiment, the impression station includes a rotatable impressioncylinder and a rotatable pressure cylinder, configured to transfer theink image to the target substrate, and the processor is configured,based on the signals, to control at least one operation selected from alist consisting of (a) timing of engagement and disengagement betweenthe impression and pressure cylinders, (b) a motion profile of at leastone of the impression and pressure cylinders, and (c) a size of a gapbetween the disengaged impression and pressure cylinders. In anotherembodiment, the processor is configured to control, based on thesignals, a drying process applied by at least one of the dryingassemblies for drying the ink droplets deposited on the ITM. In yetanother embodiment, the processor is configured to control, based on thesignals, a velocity of one or more rollers of the ITM guiding system.

In some embodiments, the processor is configured to control, based onthe signals, at least one of a cooling process, a cleaning process and atreatment process of the ITM at the ITM treatment station. In otherembodiments, the processor is configured to control, based on thesignals, application of a treatment fluid on the ITM at the ITMtreatment station. In yet other embodiments, the processor is configuredto control, based on the signals, at least one imaging parameter of adigital image of the ink image acquired and processed by the imagequality control station.

In an embodiment, the one or more maskers includes a continuous markerformed along at least a portion of the ITM. In another embodiment, atleast one of the markers engraved in the ITM includes filling material,which is configured to fill at least part of a structure formed in atleast one of the ITM layers. In yet another embodiment, the fillingmaterial includes magnetic material that produces a magnetic fieldbetween the magnetic material and the sensing assembly.

In some embodiments, the filling material is configured to change atleast one optical property of at least one of the ITM layers, or tochange at least one optical property of the entire ITM. In otherembodiments, the filling material includes at least one material from alist of materials consisting of a silicone polymer, a polyurethane, ametal, a silicone-based pigment, and a magnetic material. In yet otherembodiments, the filling material has at least one attribute selectedfrom a list of attributes consisting of: chemical affinity to a siliconepolymer, mechanical and chemical stability at a temperature rangebetween 0° C. and 180° C., chemical resistance, and surface hardnesslarger than 30 Shore A.

In an embodiment, the stack of multiple layers includes at least a firstlayer and a second layer, which is disposed on the first layer, and atleast one of the markers is engraved through the second layer and isextended into the first layer. In another embodiment, the stack ofmultiple layers includes at least a first layer and a second layer,which is disposed on the first layer, and wherein at least one of themarkers is engraved into at least part of at least one of the first andsecond layers.

There is additionally provided, in accordance with an embodiment of thepresent invention, a system that includes a flexible intermediatetransfer member (ITM), one or more sensing assemblies, and a processor.The flexible ITM includes (a) a stack of multiple layers, and (b) one ormore markers integrated with at least one of the flexible layers at oneor more respective marking locations along the ITM, the ITM isconfigured to receive ink droplets from an ink supply system to form anink image thereon, and to transfer the ink image to a target substrate.The one or more sensing assemblies are disposed at one or morerespective predefined locations relative to the ITM, and are configuredto produce signals indicative of respective positions of the markers.The processor is configured to receive the signals, and, based on thesignals, to control a deposition of the ink droplets on the ITM.

In some embodiments, the markers include one or more three-dimensional(3D) mmarkers printed on at least one of the flexible layers.

There is further provided, in accordance with an embodiment of thepresent invention, a method for producing an intermediate transfermember (ITM), the method includes providing one or more layers. One ormore markers are formed in at least one of the one or more layers so asto constitute an integral part thereof.

In some embodiments, providing the one or more layers includes providingat least (a) an opaque layer for attenuating intensity of lightimpinging thereon, and (b) a transparent layer for passing intensity oflight impinging thereon. In other embodiments, forming the one or moremarkers includes removing at least part of the opaque layer andretaining at least part of the transparent layer. In yet otherembodiments, forming the markers includes engraving at least one of themarkers into at least part of at least one of the one or more layers.

There is additionally provided, in accordance with an embodiment of thepresent invention, an intermediate transfer member (ITM) configured forreceiving ink droplets to form an ink image thereon and thr transferringthe ink image to a target substrate, the ITM includes one or more layersand one or more markers integrated with at least one of the one or morelayers at one or more respective marking locations along the ITM.

In some embodiments, at least one of the markers engraved in the ITMincludes filling material, which is configured to fill at least part ofa structure formed in at least one of the ITM layers. In otherembodiments, at least one of the markers includes an ink marker, whichis printed on at least one of the flexible layers. In yet otherembodiments, at least one of the markers includes one or morethree-dimensional (3D) markers printed on at least one of the flexiblelayers.

In an embodiment, the one or more layers include an opaque layer, whichis configured to attenuate intensity of light impinging thereon, frombeing transmitted therethrough, at least part of the opaque layer isremoved at one or more of the respective marking locations. In anotherembodiment, the one or more layers include at least: (a) anon-reflective layer, which is configured to attenuate intensity oflight impinging thereon, from being reflected therefrom, and (b) atransparent layer, which is configured to pass intensity of lightimpinging thereon. In yet another embodiment, the one or more layersinclude a non-reflective layer, which is configured to attenuateintensity of light impinging thereon, from being reflected therefrom, atleast part of the non-reflective layer is removed at one or more of therespective marking locations.

In some embodiments, at least one of the layers is folded along a lengthaxis and having first and second ends coupled to one another so as toform a continuous loop. In other embodiments, the continuous loop isconfigured to wrap around one or more rollers of an indirect printingsystem and to be guided by the rollers. In yet other embodiments, theITM is configured to wrap around one or more drums of an indirectprinting system. In some embodiments, at least one of the markers isengraved into at least part of at least one of the one or more layers.

In an embodiment, the continuous loop is configured to transfer the inkimage to the target substrate, which is selected from a list consistingof: a sheet and a continuous web. In another embodiment, at least two ofthe layers are aligned with one another and have common first and secondends, and the at least two layers are folded along a length axis, andthe first and second ends are coupled to one another so as to form acontinuous loop. In yet another embodiment, the markers are configuredto indicate an amount of stretching of the ITM.

There is additionally provided, in accordance with an embodiment of thepresent invention, an intermediate transfer member (ITM) configured forreceiving ink droplets to form an ink image thereon and thr transferringthe ink image to a target substrate, the ITM includes one or more layersand one or more markers engraved in at least one of the layers at one ormore respective marking locations along the ITM.

There is further provided, in accordance with an embodiment of thepresent invention, an intermediate transfer member (ITM), one or moresensing assemblies, and a processor. The ITM includes (a) one or morelayers, and (b) one or more markers integrated into at least one of theone of more layers at one or more respective marking locations along theITM. The ITM is configured to receive an ink image from an ink supplysystem, and to transfer the ink image to a target substrate. The one ormore sensing assemblies are disposed at one or more respectivepredefined locations relative to the ITM, and are configured to producesignals indicative of respective positions of the markers. The processoris configured to receive the signals, and, based on the signals, tocontrol a placement of the ink image on the ITM.

In some embodiments, the ITM is configured to stretch, and, based on thesignals, the processor is configured to estimate an amount of stretchingof the ITM.

There is additionally provided, in accordance with an embodiment of thepresent invention, a printing system that includes an intermediatetransfer member (ITM), one or more sensing assemblies, and a processor.The ITM includes (a) one or more layers, and (b) one or more markersintegrated into at least one of the one of more layers at one or morerespective marking locations along the ITM, the ITM is configured toreceive an image of a printing fluid from an image forming stationconfigured to supply the printing fluid, and to transfer the image to atarget substrate. The one or more sensing assemblies are disposed at oneor more respective predefined locations relative to the ITM, and areconfigured to produce signals indicative of respective positions of themarkers. The processor is configured to receive the signals, and, basedon the signals, to control a placement of the image on the ITM.

In some embodiments, at least one of the one or more layers includes atleast one material selected from a list consisting of apolytetrafluoroethylene, a polyester, a polyimide, a polyvinyl chloride(PVC), a polyolefin, an elastomer, a polystyrene-based polymer, apolyamide-based polymer, a methacrylate-based elastomer, a rubber, apolyurethane, a polycarbonate and an acrylic. In other embodiments, theprinting fluid includes a liquid including at least one colorant. In yetother embodiments, the printing fluid includes one or more types ofcolorant-containing slurries.

In an embodiment, the printing fluid includes an ink. In anotherembodiment, the printing fluid includes a toner. In yet anotherembodiment, the ITM is configured to perform a process or a combinationof processes selected from a list consisting of: (a) inkjet, (b)electmphotography, (c) lithography, (d) flexography, and (e) gravure.

There is further provided, in accordance with an embodiment of thepresent invention, an intermediate transfer member (ITM) configured forreceiving ink droplets to form an ink image thereon, for transferringthe ink image to a target substrate, and for moving along a continuouspath, the ITM includes first and second longitudinal edges, and one ormore guiding elements. The first and second longitudinal edges areextending along a longitudinal axis of the ITM. The one or more guidingelements are arranged along at least one of the first and secondlongitudinal edges and are configured to engage with a guiding subsystemof a printing system, so as to move the ITM along the continuous path.At least one of the guiding elements includes one or more markerspositioned at one or more respective marking locations along therespective guiding element.

In some embodiments, the guiding elements include one or more lateralformations formed along the first and second longitudinal edges. Theformations are configured to engage with respective guiding tracks ofthe guiding subsystem, so as to apply at least a longitudinal force tothe ITM, and at least one of the lateral formations includes at leastone of the markers. In other embodiment, at least two of the lateralformations are positioned at a predefined spacing from one another alongat least one of the first and second longitudinal edges. In yet otherembodiments, at least one of the guiding elements includes a zipfastener, and the lateral formations include teeth of the zip fastener.

In an embodiment, one or more of the teeth serve as the markers. Inanother embodiment, at least one of the teeth has a longitudinal markerdimension that is between 0.003% and 0.05% of a longitudinal ITMdimension of the ITM, and the longitudinal marker dimension and thelongitudinal ITM dimension are measured along the longitudinal axis ofthe ITM. In yet another embodiment, the zip fastener includes more than500 teeth, and one or more of the teeth serve as the markers.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a digital printing system, inaccordance with an embodiment of the present invention;

FIGS. 2A, 2B, and 2C are schematic side views of position sensingassemblies, in accordance with an embodiment of the present invention;

FIGS. 3A, 3B, and 3C are schematic side views of position sensingassemblies, in accordance with another embodiment of the presentinvention;

FIGS. 4A, 4B, 4C and 4D are schematic top views of blankets of a digitalprinting system, in accordance with several embodiments of the presentinvention;

FIGS. 5A, 5B, and 5C are schematic sectional views of blankets of adigital printing system, in accordance with several embodiments of thepresent invention;

FIGS. 6 and 7 are schematic sectional views of process sequences forproducing markers in a blanket of a digital printing system, inaccordance with several embodiments of the present invention; and

FIG. 8 is a schematic sectional view of a position sensing assembly, inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Embodiments of the present invention that are described hereinbelowprovide methods and apparatus for enhancing the precision of a digitalprinting system.

In some embodiments, the digital printing system comprises a movingflexible intermediate transfer member (ITM), also refers to herein as ablanket, and several stations, such as an image forming station, an inkdrying station and an impression station, and between which the ITMrotates by means of a guiding system. The image forming stationcomprises a plurality of print bars configured to apply ink droplets tothe ITM to form an image. The ink drying station is configured to drythe ink image applied to the ITM, and the impression station isconfigured to transfer the ink image from the ITM to a target substratesuch as a sheet of paper or a continuous web.

The digital printing system may further comprise a blanket treatmentstation, at which the blanket is cleaned, cooled and treated using atreatment fluid, before returning to the image forming station.

The digital printing system further comprises a processor configured tocontrol the operation of these stations and other components of thedigital printing system. In a printing process, it is important toaccurately deposit ink droplets on the ITM to precisely form an inkimage, and subsequently, to transfer the ink image from the ITM to thetarget substrate in a precise manner. The precision of the printingprocess rely, among other factors, on the ability to monitor themovement and the behavior (e.g. stretching) of the ITM as precisely andcontinuously as possible.

In principle, it is possible to attach labels to the ITM surface, and tocontrol the movement of the ITM using the labels, but such labels maydeteriorate in time (e.g., peel-off or erode) due to high duty cycle ofthe ITM operation in the printing process. In the disclosed embodiments,at least some of the markers are formed in the ITM and are used for thecontrol of the ITM.

In some embodiments, the ITM comprises an integrated encoder comprisinga set of markers that may be formed during the production of the ITMusing various techniques, such as forming structures in the ITM layersor on its surface, by engraving the markers, and/or jetting ink and/orprinting three-dimensional (3D) structures on one or more layers of theITM, or a combination thereof. For example, a marker may be formed byengraving a trench in the ITM surface, and subsequently, printing 3Dstructures in the trench.

In some embodiments, a processor of the digital printing system isconfigured to receive, from sensors that are mounted at one or morelocations relative to the ITM, signals indicative of positions ofrespective encoder markers. The processor is further configured tocontrol, based on the signals, a motion profile (e.g., speed,acceleration, and deceleration) of the ITM, by controlling rollers anddancers of the digital printing system, which are configured to move theITM.

In some embodiments, engraving the markers in the ITM surface may becarried out using any suitable technique, such as laser marking, laserablating, and/or direct part marking (e.g., mechanical punching and/orpinning). The engraved markers may have any suitable size and shape offootprint (e.g., round, rectangular, square, or star shapes shown in atop-view) profile (e.g., hole, trench, or staircase shapes, shown in asectional view).

In some embodiments, the engraved markers may be fully or partiallyfilled with a suitable filling material, so as to provide the markerswith mechanical support, and to add features to the markers of theencoder. For example, the filling materials may change the magneticproperties of the ITM by applying magnetic materials to the engravedmarkers and/or to the ITM surface. Alternatively or additionally, thefiling materials may change the optical properties of the engravedmarkers and/or of the ITM surface and/or of at least one layer of theITM by adding various types of pigments, e.g., to the filling materials.

In some embodiments, the encoder may comprise various types of encodedstructures that may serve as markers, such as grid markers, quickresponse (QR) codes, AZTEC codes, or a combination thereof. Thesemarkers may be sensed using any suitable type of sensors, such asoptical-based sensors (e.g., visible light, infrared, ultraviolet) ormagnetic-based sensors.

In some embodiments, one or more encoders are typically located at thebevels of the ITM and may comprise various types of markers, interleavedwith one another along the ITM. Additionally, or alternatively, markersof different types may be grouped at different respective locations ofthe ITM.

The disclosed techniques improve the quality of printed images byaccurately controlling a plurality of operations of the digital printingsystem, such as the deposition of ink droplets on the ITM so as to formthe ink image, the drying of the ink droplets, the transfer of the inkimage from the ITM to a target substrate and the treatment of the ITMbefore returning to the image forming station. The disclosed techniquemay be used to reduce the complexity of the digital printing system, forexample, by reducing the need to integrate rotary encoders to therollers. Moreover, the disclosed encoders are designed and produced todemonstrate high endurance even at high duty cycles typically used indigital printing systems.

System Description

FIG. 1 is a schematic side view of a digital printing system 11, inaccordance with an embodiment of the present invention. In someembodiments, system 11 comprises a rolling flexible blanket 210 thatcycles through an image fhnning station 212, a drying station 214, animpression station 216 and a blanket treatment station 50. In thecontext of the present invention and in the claims, the terms “blanket”and “intermediate transfer member (ITM)” are used interchangeably andrefer to a flexible member comprising a stack of layers used as anintermediate member configured to receive an ink image and to transferthe ink image to a target substrate, as will be described in detailbelow.

In some embodiments, image forming station 212 is configured to supplyvarious types of printing fluids, such as any suitable type of ink (e.g.inkjet ink), and/or liquid toner and/or colorant-containing slurries,and other liquids that include at least one colorant. The descriptionbelow refers to aqueous ink but is also applicable for any other type ofprinting fluid.

In an operative mode, image forming station 212 is configured to form amirror ink image, also referred to herein as “an ink image” (not shown),of a digital image 42 on an upper run of a surface of blanket 210.Subsequently the ink image is transferred to a target substrate, (e.g.,a paper, a folding carton, or any suitable flexible package in a form ofsheets or continuous web) located under a lower run of blanket 210.

In the context of the present invention, the term “run” refers to alength or segment of blanket 210 between any two given rollers overwhich blanket 210 is guided.

In some embodiments, during installation blanket 210 may be adhered edgeto edge to form a continuous blanket loop (not shown) by soldering,gluing, taping (e.g. using Kapton® tape, Room-Temperature-Vulcanizingsilicone (RTV) liquid adhesives or thermoplastic adhesives with aconnective strip overlapping both edges of the strip), or using anyother suitable method. Any method of joining the ends of blanket 210 maycause a discontinuity, referred to herein as a seam, and it is desirableto avoid an increase in the thickness or discontinuity of chemicaland/or mechanical properties of blanket 210 at the seam. One example ofa method and a system for the installation of the seam is described indetail in U.S. Provisional Application 62/532,400, whose disclosure isincorporated herein by reference.

In some embodiments, image forming station 212 comprises four separateprint bars 222, connected to an ink supply system, each of which isconfigured to deposit one of four different colors, such as cyan (C),magenta (M), yellow (Y) and black (K). In other embodiments, station 212may comprise any suitable number of print bars 222 arranged in station212 at any suitable configuration and spacing therebetween. The inksupply system further comprises multiple ink reservoirs (not shown)configured to supply the cyan (C), magenta (Ni), yellow (Y) and black(K) aqueous ink to print bars 222. In other embodiments, the ink supplysystem may comprise more than one ink reservoir for each color, andoptionally additional ink reservoirs for additional colors not mentionedabove.

In some embodiments, each of print bars 222 incorporates one or moreprint heads configured to jet ink droplets of different colors onto thesurface of blanket 210 so as to form the ink image (not shown) on thesurface of blanket 210.

In some embodiments, print bars 222 are configured to deposit differentshades of the same color, such as various shades of gray includingblack, or for two or more print bars 222 to deposit the same color,e.g., black.

In some embodiments, system 11 may comprise drying stations 224 that maybe located between print bars 222 also referred to herein asintermediate drying stations (not shown) and/or after image formingstation 212 as shown in FIG. 1. Drying stations 224 are configured toblow hot air (or another gas) onto the surface of blanket 210, so as topartially dry the ink image that is being formed.

This hot air flow between the print bars may assist, for example, inreducing condensation at the surface of the print heads and/or handlingsatellites (e.g., residues or small droplets distributed around the mainink droplet), and/or in preventing blockage of the inkjet nozzles of theprint heads, and also prevents the droplets of different color inks onblanket 210 from undesirably merging into one another. In someembodiments, each print bar 222 is configured to jet one or moredroplets of the same color at a given location on blanket 210, so as tocontrol the level of printed color at the given location. For example,one droplet of black ink may result in light grey printed color, whereasthree droplets of black ink deposited on blanket 210 may result in darkgrey or black color at the given location.

In drying station 214, the ink image formed on blanket 210 is exposed toradiation and/or hot air in order to dry the ink more thoroughly,evaporating most of the liquid carrier and leaving behind only a layerof resin and coloring agent which is heated to the point of beingrendered tacky.

In impression station 216, blanket 210 passes between an impressioncylinder 220 and a pressure cylinder 218, which is configured to carry acompressible blanket 219.

In some embodiments, system 11 comprises a control console 12, which isconfigured to control multiple stations and other components of system11, such as the motion of blanket 210, image forming station 212, andother components described herein. In some embodiments, console 12comprises a processor 20, typically a general-purpose processor, withsuitable front end and interface circuits for controlling, for example,the motion of blanket 210 and station 212, and for receiving signalstherefrom. In some embodiments, processor 20 may be programmed insoftware to carry out the functions that are used by the printingsystem, and the processor stores data for the software in a memory 22.The software may be downloaded to processor 20 in electronic form, overa network, for example, or it may be provided on non-transitory tangiblemedia, such as optical, magnetic or electronic memory media.

In some embodiments, console 12 comprises a display 34, which isconfigured to display data and images received from processor 20, orinputs inserted by a user (not shown) using input devices 40 of system10. In some embodiments, console 12 may have any other suitableconfiguration, for example, an alternative configuration of console 12and display 34 is described in detail in U.S. Pat. No. 9,229,664, whosedisclosure is incorporated herein by reference.

In some embodiments, processor 20 is configured to display on display34, digital image 42 comprising one or more segments of a pattern of animage stored in memory 22. The pattern is stored in one or more digitalfiles for defining characteristics of the image to be printed by system11.

In some embodiments, system 11 comprises one or more electricaldistribution boards 235, configured to electrically connect betweenconsole 12 and all the components, modules and stations of system 11. Itwill be understood that the configurations of the electrical cabling androuting of system 11 is simplified and depicted purely by way ofexample, and other suitable configurations can also be used.

In some embodiments, blanket treatment station 50, also referred toherein as a cooling station, is configured to treat the blanket by, forexample, cooling it and/or applying a treatment fluid to the outersurface of blanket 210, and/or cleaning the outer surface of blanket210. At blanket treatment station 50 the temperature of blanket 210 canbe reduced to a desired value before blanket 210 enters image fformingstation 212. The treatment may be carried out by passing blanket 210over one or more rollers or blades configured for applying coolingand/or cleaning and/or treatment fluid on the outer surface of theblanket. In some embodiments, the processor 20 is configured to receive,e.g., from temperature sensors (not shown), signals indicative of thesurface temperature of blanket 210, so as to monitor the temperature ofblanket 210 and to control the operation of blanket treatment station50. Examples of such treatment stations are described, for example, inPCT International Publications WO 2013/132424 and WO 2017/208152, whosedisclosures are all incorporated herein by reference.

In the example of FIG. 1, station 50 is mounted between rollers 252 and253, yet, station 50 may be mounted adjacent to blanket 50 at any othersuitable location between impression station 216 and image formingstation 212.

Sheets 226 or continuous web (not shown) are carried by a suitabletransport mechanism (not shown) from a supply stack 228 and passedthrough a nip located between impression cylinder 220 and pressurecylinder 218. Within the nip, the surface of blanket 210 carrying theink image is pressed finely by compressible blanket 219 of pressurecylinder 218 against sheet 226 (or other suitable substrate) so that theink image is impressed onto the surface of sheet 226 and separatedneatly from the surface of blanket 210. Subsequently, sheet 226 istransported to an output stack 230.

In some embodiments, print bars 222 are positioned at predefined spacingfrom one another along a movement axis of blanket 210, represented by anarrow 290. In some embodiments, system 11 further comprises varioustypes of rollers, such as rollers 232, 240, 242 and 253. In anembodiment, at least some of these rollers are controlled by processor20 of console 12, so as to enable movement of blanket 210 at a desired(typically constant) speed below image forming station 212. Note thatunsmooth or vibrating movement of blanket 210 may affect deposition ofthe ink image comprising one or more of the colors, and typically affectthe accuracy of color-to-color registration.

In some embodiments, system 11 comprises two powered tensioning rollers,also referred to as dancers 250 and 252. Dancers 250 and 252 areconfigured to control the length of slack in blanket 210 before andafter the nip and their movement is schematically represented by doublesided arrows adjacent to the respective dancers. Furthermore, anystretching of blanket 210 with aging would not affect the ink imageplacement performance of system 11 and would merely require the takingup of more slack by tensioning dancers 250 and 252.

In some embodiments, a rotary encoder (shown for example in FIG. 2Abelow) is incorporated into at least one of rollers 232, 240, 242 and253, and dancers 250 and 252. The rotary encoder is configured toproduce rotary-based position signals indicative of an angulardisplacement of the respective roller or dancer.

The configuration and operation of rollers 232, 240, 242 and 253, anddancers 250 and 252 are described in further detail, for example, inU.S. Patent Application Publication 2017/0008272 and in theabove-mentioned PCT International Publication WO 2013/132424, whosedisclosures are all incorporated herein by reference.

In some embodiments, blanket 210 comprises an encoder comprising one ormore markers 33 formed (e.g., engraved) along the blanket as shownschematically in FIG. 1 and depicted in several embodiments in FIGS. 2-7below. Note that markers 33 may be distributed over blanket 210 in anysuitable configuration or embedded within one or more of the blanketlayers, as described below. Furthermore, the encoder may comprise,instead of or in addition to markers 33, at least one continuous marker(not shown) formed along at least a portion of blanket 210. Thecontinuous marker may be produced, for example, by jetting ink on topof, or between, the layers of blanket 210, or by using any othersuitable technique as will be described in detail below.

In some embodiments, system 11 further comprises multiple sensingassemblies such as, for example, eight sensing assemblies 55A . . . 55Hin the figure, disposed at one or more respective predefined locationsadjacent to blanket 210. The sensing assemblies are configured toproduce, in response to sensing markers 33, electrical signals, such asposition signals indicative of respective positions of markers 33. Inthe example configuration of FIG. 1, sensing assembly 55A is disposedabove roller 242 so as to produce position signals indicative ofrespective positions of markers 33 engraved at a given section of movingblanket 210 before the given section moves below image forming station212. In the context of the present invention and in the claims, the term“signals” may refer to various types of electrical signals, such asposition signals, sensed by the sensing assemblies.

In some embodiments, sensing assembly 55B may be coupled to cyan (and/orany other) print bar 222 labeled ‘C’, sensing assembly 55C disposedbetween print bars 222 labeled ‘M’ and ‘K’, sensing assemblies 55D and55E are respectively positioned before and after drying station 214, andsensing assemblies 55F-55H are fixed at various positions adjacent tothe lower run of blanket 210. In other embodiments, system 11 maycomprise any other suitable number of sensing assemblies 55 fixed at anysuitable positions adjacent to blanket 210.

In some embodiments, one or more similar or different sensing assembliesmay be associated with one or more of the stations along printing system11, e.g. image formation station 212, drying station 214, impressionstation 216, blanket treatment station 50, and other station of system11, and can be located at any locations adjacent to these stationsallowing to produce signals as mentioned above.

In some embodiments, sensing assemblies SSA-55H are configured toproduce signals indicative of the position of each marker 33corresponding to incremental motion of blanket 210. In an embodiment,sensing assemblies 55A-55H are electrically connected to processor 20,which is configured to receive these position signals, and based on theposition signals, to control several processes, such as the motion ofblanket 210.

In some embodiments, the signals received from sensing assemblies55A-5511 may be used for controlling various stations and modules ofsystem 11. For example, in station 212, these signals may be used forsetting the timing or time sequences of the ink droplets jetting, andthe waveform that sets the profile of the jetting from each print headof print bars 222. In the drying process, the signals received fromsensing assemblies 55A-55H may be used, for example, for setting thetemperature and airflow of the intermediate and drying stations 214.

In some embodiments, the signals received from sensing assemblies55A-55H may be used for controlling processes of impression station 216,for example, for controlling the timing of the engagement anddisengagement of cylinders 218 and 220 and their respective motionprofiles, for controlling a size of a gap between cylinders 218 and 220,for synchronizing the operation of impression station 216 with respectto the location the blanket seam, and for controlling any other suitableoperation of station 216.

In some embodiments, the signals received from sensing assemblies55A-55H may be used for controlling the operation of blanket treatmentstation 50 such as for controlling the cleaning process, and/or theapplication of the treatment liquid to blanket 210, and for controllingevery other aspect of the blanket treatment process.

Moreover, the signals received from sensing assemblies 55A-55H may beused for controlling the operation of all the rollers and dancers ofsystem 11, each roller individually and synchronized with one another,to control any sub-system of system 11 that controls temperatureaspects, and heat exchanging aspects of the operation of system 11. Insome embodiments, the signals received from sensing assemblies 55A-55Hmay be used for controlling blanket imaging operations of system 11. Forexample, based on data obtained from an image quality control station(not shown) configured to acquire digital images of the image printed onthe target substrate, for controlling the operation of any othercomponent of system 11.

In the example of FIG. 1, rollers 232 are positioned at the upper run ofblanket 210 and are configured to maintain blanket 210 taut when passingadjacent to image forming station 212. Furthermore, it is particularlyimportant to control the speed of blanket 210 below image thnningstation 212 so as to obtain accurate jetting and deposition of the inkdroplets, thereby placement of the ink image, by forming station 212, onthe surface of blanket 210.

In some embodiments, impression cylinder 220 is periodically engaged toand disengaged from blanket 210 to transfer the ink images from movingblanket 210 to the target substrate passing between blanket 210 andimpression cylinder 220. In some embodiments, the periodic engagementsinduce mechanical vibrations within slack portions in the lower run ofblanket 210. System 11 is configured to apply torque to blanket 210using the aforementioned rollers and dancers, so as to maintain theupper run taut and to substantially isolate the upper run of blanket 210from being affected by the mechanical vibrations in the lower run.

In some embodiments, based on the position signals received from sensingassemblies 55A-55H, processor 20 is configured to control the torqueapplied to blanket 210 by each roller and dancer, so as to maintain theupper run of blanket 210 taut and isolated from being affected by themechanical vibrations at the lower run. For example, drying station 214applies radiation and/or hot air to blanket 210, so as to dry the inkimage formed by image forming station 212. In some cases the appliedradiation and/or hot air may cause thermal expansion of blanket 210 whenpassing under drying station 214. In some embodiments, processor 20 isconfigured to receive an indication of the thermal expansion based onthe position signals produced by sensing assemblies 55D and 55E locatedbefore and after station 214. Based on the position signals sensed bysensing assemblies 55D and 55E, processor 20 is configured to set thetorque level at rollers 240, 232 and 242 so as to maintain blanket 210taut and moving at a specified speed under image forming station 212 anddrying station 214.

In another embodiment, based on position signals received from sensingassemblies 55G and 55F, processor 20 is configured to set the torquelevels applied to blanket 210 by dancers 250 and 252 and by rollers 253,so as to maintain blanket 210 taut and moving in accordance with aspecified motion profile (e.g., speed, acceleration and deceleration) inimpression station 216 and in other rollers guiding blanket 210. Notethat processor 20 is configured to coordinate between the motionprofiles of cylinders 218 and 220, and also to control the engagementand disengagement carried out therebetween.

In some embodiments, processor 20 is further configured to synchronizebetween the operation of print bars 222 directing the ink droplets, andthe actual instantaneous speed at which blanket 210 moves below imageforming station 212, based on the position signals received from sensingassemblies 55A-55D, so as to enable correct deposition of the ink imageon the surface of blanket 210.

In some embodiments, processor 20 is further configured to controladditional process steps that are carried out during the digitalprinting process by several stations and modules of system 11. Forexample, controlling the process of jetting ink droplets by imageforming station 212, controlling the operation of drying station 214 soas to dry the ink image by applying to blanket 210 suitable amount ofheat at precise timing, controlling the blanket treatment stationconfigured to apply a treatment fluid to blanket 210, controlling theoperation of impression cylinder 220 and pressure cylinder 218 so as toenable precise transfer of the ink image from blanket 210 to arespective sheet 226.

In the example of FIG. 1, sensing assemblies 55A-55F are mountedexternally to a loop formed by blanket 210, and sensing assemblies 55Gand 55H are mounted internally to the loop. This configuration isprovided by way of example, so as to show two different types of sensingassemblies 55 depicted in detail in FIGS. 2A-2C and 3A-3C below. Inother exemplary configurations, system 11 may comprise any suitablenumber of different types of sensing assemblies. The sensing assembliesmay be mounted adjacent to blanket 210 at any suitable configuration.

The configuration of system 11 is simplified and provided purely by wayof example for the sake of clarifying the present invention. Thecomponents, modules and stations described in printing system 11hereinabove and additional components and configurations are describedin detail, for example, in U.S. Pat. Nos. 9,327,496 and 9,186,884, inPCI international Publications WO 2013/132438, WO 2013/132424 and WO2017/208152, in U.S. Patent Application Publications 2015/0118503 and2017/0008272, whose disclosures are all incorporated herein byreference.

In some embodiments, the signals received from sensing assemblies55A-55H may be used for controlling the operation of stations, modulesand components of other configurations of digital printing systems usingany suitable type of ITM to carry out digital printing processes. Forexample, for controlling systems configured to print on a continuousweb, and systems configured to print on both sides of the sheet, alsoreferred to as duplex printing systems. These web printing and duplexprinting systems may comprise, additionally or alternatively to theconfiguration of system 11, various modules and stations, such asmultiple impression stations 216 and different configurations of rollersand dancers. Exemplary modules and stations of such web printing andduplex printing systems are described in detail, for example, in PCTInternational Publication WO2013/132424 and in U.S. Patent ApplicationPublication 2015/0054865, whose disclosures are all incorporated hereinby reference.

In other embodiments, image fomiing station 212 is configured to applythe printing fluid (e.g., ink, toner) by jetting droplets as describedabove, or using any other suitable indirect printing technique. Forexample, image forming station 212 may comprise a photo charging stationconfigured to apply an electrostatic charge image representing the imageto be printed, and one or more colors of printing fluids that compriseelectrically charged particles that attract to the opposing electricalfields applied to the surface of a transfer member (e.g. blanket 210 ora drum). Subsequently, the transfer member is configured to transfer theimage to sheet 226 or to any other target substrate as described above.

The particular configurations of system 11 is shown by way of example,in order to illustrate certain problems that are addressed byembodiments of the present invention and to demonstrate the applicationof these embodiments in enhancing the performance of such systems.Embodiments of the present invention, however, are by no means limitedto this specific sort of example systems, and the principles describedherein may similarly be applied to any other sorts of printing systemsthat are known in the art, in particular printing systems using anintermediate transfer member, i.e. indirect printing systems which use,for example, a blanket or a drum to transfer the image to be printed,offset printing systems (e.g, using lithography, flexography, andgravure techniques), digital printing systems (i.e. inkjet andelectrophotography), or any combination of such systems. In someembodiments, the ITM is configured to perform a process or a combinationof processes, such as but not limited to inkjet, electrophotography,lithography, flexography and gravure. In these embodiments, the printingsystem may comprise any type of an offset printing system (e.g., usinglithography, and/or flexography and/or gravure processes), or any typeof a digital printing system (e.g., using inkjet and/orelectrophotography processes), or any combination thereof.

Producing Signals Indicative of Respective Positions of MarkersIntegrated into the Blanket

FIG. 2A is a schematic side view of a position sensing assembly 260, inaccordance with an embodiment of the present invention. In someembodiments, assembly 260 may replace, for example, any sensing assemblyamong sensing assemblies 55A-55H of FIG. 1 above. As described in FIG. 1above, blanket 210 comprises multiple markers 33, which may be formed inblanket 210 and constitute an integral part thereof using any suitableprocessing technique.

In some embodiments, blanket 210 comprises multiple layers, such as alayer 273, which may be transparent to at least some wavelengths oflight, and a layer 277, which is typically opaque to light. In thecontext of the present invention and in the claims, the term “opaquelayer” refers to a layer adapted to attenuate substantial intensity oflight impinging thereon, from being transmitted therethrough.

Furthermore, in the context of the present invention, the term“transparent layer” refers to a layer adapted to pass substantialintensity of the light impinging thereon, and the term “non-reflectivelayer” refers to a layer adapted to attenuate substantial intensity ofthe impinging thereon from being reflected therefrom. It will beunderstood that the opaqueness, transparency and reflectivity propertiesof a layer depend on various parameters, such as layer thickness and thewavelength of the light impinging on the respective layer.

Detailed embodiments related to structures of the stacked layers of anysuitable blanket, such as blanket 210, are provided for example, inFIGS. 6 and 7 of the present invention, and in PCT InternationalPublications WO 2017/208144, whose disclosure is incorporated herein byreference.

In some embodiments, marker 33 may be formed by engraving blanket 210 atintended locations, also referred to herein as marking locations, at oneor more of the blanket layers, at any suitable stage of the blanketproduction process, such that at least opaque layer 277 is partiallyremoved and at least one transparent layer, such as layer 273, isremained in the stack.

The engraved configuration of marker 33 allows passage of at least aportion of light, whereas the sections of blanket 210 having at leastone opaque layer are configured to block the light from reaching sensingassembly 260 or any other suitable light sensing assembly.

In these embodiments, marker 33 may be produced using any suitableprocess, such as but not limited to, laser marking, laser ablating,laser engraving, direct part marking (DPM) using punching or pinningtechniques, ink-jetting, three-dimensional (3D) printing, disposingmagnetic materials, forming a mixture of magnetic pigments in the stackof layers, or any other suitable processing technique. In someembodiments, the surface of marker 33 may be further processed so as toform different levels of surface roughness and textures, using anysuitable technique, such as but not limited to mechanical processing,chemical processing, and laser processing, e.g., thermal ablation.

Note that using one or more of the above techniques, enables theformation of an encoder integrated with the structure of blanket 210,e.g., by removing opaque layers from blanket 210, by disposing suitablematerial between the layers of blanket 210, and/or by disposing material(e.g., ink-jetting, 3D printing) on the surface of one or more layers ofblanket 210.

As described in FIG. 1 above, the rollers and dancers are configured tomove blanket 210 along the movement axis represented by arrow 290. Inthe example of FIG. 2A, each of rollers 266 and 268 may replace any ofthe rollers and dancers described in FIG. 1 above, are configured tomove blanket 210 along the movement axis.

In some embodiments, a rotary encoder 272 is incorporated into roller266 and is configured to produce rotary-based position signalsindicative of an angular displacement of roller 266. Encoder 272 isfurther configured to provide processor 20 with these rotary-basedposition signals so as to improve the motion control of blanket 210.

In some embodiments, position sensing assembly 260 comprises anysuitable type of a light source, in the present example a light emittingdiode (LED) 262, which is configured to emit light beams 264, having anysuitable wavelength or range of wavelengths, through an aperture (notshown) mounted on an upper surface 265 of LED 262.

In the example of FIG. 2A, LED 262 is mounted relative to blanket 210,such that surface 265 is substantially parallel to a lower surface 267of blanket 210, and substantially orthogonal to an axis 263 of LED 262.

In some embodiments, position sensing assembly 260 further comprises asensor 271, which is configured to sense light beams 264 emitted fromLED 262, and to produce position signals indicative of the position ofeach marker 33 in any suitable coordinate system and/or relative to anyreference point in system 11. In an embodiment, light beams 264 may haveany wavelength or range of wavelengths within the range of visible light(i.e., 400 nm-700 nm). In another embodiment, light beams 264 may have awavelength or range of wavelengths within the range of infrared (IR)(i.e., 700 nm-1 mm) or ultraviolet (LW) (i.e., 10 nm-400 nm). In theconfiguration of assembly 260, light beams 264 is also referred toherein as “backlight” or “diffused light.”

In some embodiments, position sensing assembly 260 further comprises aslit 274, which is mounted between blanket 210 and sensor 271. In anembodiment, slit 274 has an opening 275, or a plurality of such opening,configured to pass at least a portion of light beams 264 to sensor 271.

During the operation of system 11, blanket 210 moves in the direction ofarrow 290 and light beams 264 impinges on surface 267 of blanket 210.When sections of blanket 210 that comprise the full stack of layers passabove LED 262, light beams 264 is blocked by layer 277 and therefore,cannot be sensed by sensor 271. In contrast, when a section comprisingmarker 33 passes above LED 262, at least some beams of light beams 264may pass through transparent layer 273 and sensed by sensor 271.

Note that position sensing assembly 260 produces the position signals bysensing the beams of light beams 264 that are transmitted by LED 262,and pass through transparent layers (e.g., layer 273) of blanket 210,engraved marker 33 and opening 275 of slit 274 to reach sensor 271. Inother embodiments, the light may be reflected by, rather than passingthrough marker 33, as will be described in FIGS. 3A and 3B below.

FIG. 2B is a schematic side view of a position sensing assembly 270, inaccordance with an embodiment of the present invention. In someembodiments, assembly 270 may replace, for example, any sensing assemblyamong sensing assemblies 55A-55H of FIG. 1 above. In some embodiments,assembly 270 and assembly 260 have similar configurations, which differmainly in regard to the LED configuration. In some embodiments, LEI) 262is mounted in position sensing assembly 270, such that an axis 269 ofLED 262 is tilted at a predefined angle 276 relative to axis 263. Thisconfiguration may improve, for example, the operation, as well as theease of production and serviceability of assembly 270.

During the operation of system 11, in a time period in which blanket 210moves in the direction of arrow 290, LED 262 is configured to emit lightbeams 264 that impinges on surface 267 of blanket 210. When sections ofblanket 210 that comprise at least one opaque layer (e.g., layer 277)passes above LED 262, light beams 264 is blocked by layer 277 andtherefore, cannot reach sensor 271. When a section comprising marker 33passes above LED 262, at least some beams of light beams 264 may passthrough transparent layer 273 and sensed by sensor 271.

FIG. 2C is a schematic side view of a position sensing assembly 280, inaccordance with an embodiment of the present invention. Position sensingassembly 280 may replace, for example, any sensing assembly amongassemblies 55A-55H of FIG. 1 above.

In some embodiments, position sensing assembly 280 comprises a laser282, which is configured to emit a laser beam 286 impinging on surface267 of blanket 210. Laser beam 286 may have a wavelength selected fromone of the ranges described above, e.g., visible, IR or UV, or any othersuitable wavelength.

In an example embodiment of FIG. 2C, rollers 268 may not comprise arotary encoder, so that markers 33 may be used instead of the rotaryencoder or any other type of encoder incorporated in system 11. In anembodiment, markers 33, which constitute the encoder integrated inblanket 210, may be used in addition to, or instead of any encoder ofsystem 11. Note that in this embodiment, none of the rollers of system11 may incorporate an encoder. As described in FIG. 1 above, markers 33may be used for controlling the operation of various stations andmodules of system 11 and for controlling other configurations of systemsdescribed above, e.g., duplex printing systems and web printing systems.In another embodiment, any suitable rotary encoder, such as encoder 272shown in FIG. 2B, may be integrated into at least one of rollers 268.

In some embodiments, position sensing assembly 280 comprises a sensor284, which is configured to sense beam 286 emitted from laser 282 and,in response to sensing beam 286, to produce position signals indicativeof the position of each marker 33 relative to any reference point insystem 11. In alternative embodiments, the positions of sensor 284 andlaser 282 (e.g., an IR laser) may be swapped, such that laser 282 ispositioned above blanket 210 and directing beam 286 towards sensor 284located below layer 273 of blanket 210.

During the operation of system 11, blanket 210 moves in the direction ofarrow 290 and laser beam 286 impinges on surface 267 of blanket 210.When sections of blanket 210 that comprise the full stack of layers passabove LED 262, laser beam 286 is blocked by layer 277 and therefore,cannot be sensed by sensor 284. In contrast, when a section comprisingmarker 33 passes above laser 282, at least some intensity of laser beam286 may pass through transparent layer 273 and sensed by sensor 284.

Note that position sensing assembly 280 produces the position signals bysensing photons of laser beam 286, which are passing through transparentlayers (e.g., layer 273) of engraved marker 33 to reach sensor 284.

In some embodiments, a suitable slit (not shown), such as slit 274 shownin FIGS. 2A and 2B above, may be mounted between blanket 210 and sensor284 so as to control the attributes (e.g., angle) of photons reachingsensor 284. In some embodiments, using a laser light source may improvethe lateral resolution of sensing assembly 280, which may allow usingnarrower markers 33. Using a laser (e.g., instead of an LED) lightsource may also prevent light saturation or flooding of sensor 284, soas to improve the sensitivity of the sensor.

In some embodiments, blanket 210 is made from a stretchable material,and is therefore able to expand and shrink during the operation ofsystem 11. The amount of stretching depends on the materials of theblanket layers, and on various parameters of the printing process, suchas printing and drying temperature, motion profile (e.g., speed,acceleration, and deceleration) of blanket 210 and the like.

In some embodiments, markers 33 are integrated into blanket 210, andtherefore, are configured to reflect the blanket flexibility and extentof its stretching, and/or to indicate an amount of stretching of blanket210. For example, when blanket 210 expands e.g., by one percent, thedistance between adjacent sections of layer 277 comprising markers 33,may increase by one percent or by another amount indicative of thestretching amount of blanket 210.

In some embodiments, markers 33 have the same flexibility of blanket210, and therefore are configured to emulate the behavior of blanket210, as described in the example of one percent stretching describedabove.

In some embodiments, processor 20 is configured to receive from theaforementioned sensing assemblies, signals indicative of the stretchingamount of markers 33 and, based on the signals, to estimate the amountof stretching of blanket 210. Processor 20 is further configured toadjust various parameters of the printing process based on the estimatedstretching amount of blanket 210. For example, processor 20 may adjustthe motion profile of blanket 210 and the timing of ink jetting fromprint bars 222 applied to the surface of blanket 210.

FIG. 3A is a schematic side view of a position sensing assembly 300, inaccordance with an embodiment of the present invention. In someembodiments, assembly 300 may replace, for example, any sensing assemblyamong sensing assemblies 55A-55H of FIG. 1 above. In some embodiments,position sensing assembly 300 is configured to sense one or moremarkers, such as a marker 333 integrated into a blanket 310, and inresponse to sensing the markers, to produce position signals indicativeof the position of respective markers 333.

In some embodiments, blanket 310 comprises multiple layers, such astransparent layer 273 and opaque layer 277 depicted in FIG. 2A above.Note that opaque layer 277 is also a non-reflective layer. Blanket 310may comprise a reflective layer 379, which may be applied tonon-reflective layer 277 or to any other layer (not shown) disposedtherebetween.

In the example of FIG. 3A, marker 333 is formed by engraving a patternin layer 379. The pattern may be formed by removing material from layer379 using any suitable technique, such as laser ablating, or variousetching processes. Additionally or alternatively, marker 333 maycomprise a light-reflecting label disposed after engraving at least partof layer 333.

In some embodiments, position sensing assembly 300 comprises a sensingmodule 340 comprising a laser 306, which may have properties similar tolaser 282 of FIG. 2C above. Laser 306 is configured to emit an incidentbeam 386 directed, at a substantially right angle, or at any othersuitable angle relative to an upper surface 302 of layer 379 and onmarker 333. In some embodiments, sensing module 340 further comprises asensor 308, which may have properties similar to sensor 284 of FIG. 2Cabove, and which is configured to sense a diffused beam 387 reflectedfrom marker 333.

In some embodiments, the engraved pattern of marker 333 may comprise oneor more surfaces inclined at a predefined angle relative to surface 302,in the present example multiple triangles 334, which are configured toreflect beam 387 at an angle 312, such that beam 387 is sensed by sensor308. Note that the position of sensor 308 in sensing module 340corresponds to angle 312.

In other embodiments, layer 379 may be partially or completely removedat marker 333, and the reflective label described above may comprise theinclined surfaces and may be coupled (e.g., glued) to the laser-facingsurface of marker 333.

As described in FIG. 2C above, roller 268 is configured to move blanket310 in the moving direction shown by arrow 290, and may further compriserotary encoder 272 so as to provide processor 20 with rotary-basedposition signals, as described in FIG. 2A above.

FIG. 3B is a schematic side view of a position sensing assembly 360, inaccordance with an embodiment of the present invention. In someembodiments, assembly 360 may replace, for example, any sensing assemblyamong sensing assemblies 55A-55H of FIG. 1 above. In some embodiments,position sensing assembly 360 is configured to sense one or moremarkers, such as a marker 335 integrated into a blanket 320, and inresponse to sensing markers 335, to produce position signals indicativeof the position of respective markers 335.

In some embodiments, blanket 320 comprises multiple layers, such aslayers 277 and 379 depicted, respectively, in FIGS. 2A and 3A above.Blanket 320 further comprise a layer 373 having an upper surface 369 anda lower surface 371.

In the example of FIG. 3B, marker 335 is formed by engraving layers 379and 277, thereby exposing surface 369 to sensing assembly 360.

In some embodiments, position sensing assembly 360 comprises a sensingmodule 350 comprising laser 306, which is configured to direct incidentbeam 386, at a substantially right angle, to surfaces 302 and 369. Insome embodiments, sensing module 340 further comprises a sensor 309,which have properties similar to sensor 308 of FIG. 3A above, and whichis configured to sense a diffused beam 388 reflected from marker 335.

In some embodiments, layer 373 is transparent to beam 386, however anouter surface 368 of roller 268 is configured to reflect beam 386 and toproduce beam 388 directed to sensor 309.

FIG. 3C is a schematic side view of a position sensing assembly 390, inaccordance with an embodiment of the present invention. In someembodiments, assembly 390 may replace, for example, any sensing assemblyamong sensing assemblies 55A-55H of FIG. 1 above. In some embodiments,position sensing assembly 390 is configured to sense one or moremarkers, such as a marker 392 integrated with a blanket 330, and inresponse to sensing markers 392, to produce position signals indicativeof the position of respective markers 392.

In some embodiments, blanket 330 may have a structure of layerssubstantially similar to the structure of blanket 320 of assembly 360shown in FIG. 3B above, or any other suitable structure of layers.

In the example of FIG. 3C, marker 394 is formed by engraving a trench396 or a hole in at least part of layers 379 and 277 using the engravingmethods described above, and filling at least part of trench 396 byapplying magnetic layer 394 to layer 373. In some embodiments, magneticlayer 394 is applied into trench 396, such that an upper surface 398 ofmagnetic layer 394 is flush relative to surface 302 of blanket 330. Inother embodiments, the distance between surfaces 398 and 371 may belarger than the distance between surfaces 302 and 371, such that surface398 extends above surface 302.

In some embodiments, position sensing assembly 390 comprises a magneticsensor 319, which is configured to sense a magnetic field (not shown)produced when marker 392 passes adjacent to magnetic sensor 319. Asdescribed above, position sensing assembly 390 is configured to produce,based on the magnetic field sensed by sensor 319, position signalsindicative of the position of marker 392.

Controlling the Shape and Position of Markers Integrated Into theBlanket

FIG. 4A is a schematic top view of a blanket 400, in accordance with anembodiment of the present invention. Blanket 400 may replace, forexample, blanket 210 of system 11. In some embodiments, blanket 400comprises a flexible substrate 402 comprising a stack of multiple layers(not shown) described in detail in FIGS. 6 and 7 below. In someembodiments, substrate 402 has two edges, referred to herein as ends 404and 406 located along a Y axis, which is the width of blanket 400. Ends404 and 406 are substantially parallel to arrow 290 and are orthogonalto the Y axis.

In some embodiments, blanket 400 comprises a linear encoder 401, whichis an integral part of blanket 400 and comprises a plurality of markers408 formed during the production process of blanket 400,and separated byrespective buffers 412.

In the example of FIG. 4A, encoder 401 is formed adjacent to end 404,the position of encoder 401 is referred to herein as a bevel ofsubstrate 402 and of blanket 400, and markers 408 are interleaved withbuffers 412, such that each buffer 412 separates between two respectiveneighbor markers 408 and vice versa. Each marker 408 has a predefinedlength 415 and width 416, such that the total size of length 415 and arespective neighbor buffer 412 defines a pitch 414 of each marker 408.In the example embodiment of FIG. 4A, each marker 408 has asubstantially similar shape, size (e.g., length and width in case of arectangular-shaped) and pitch. In another embodiment, at least one ofthe shape, size, pitch and location of the marker may vary alongsubstrate 402. For example, the blanket may comprise two types ofmarkers interleaved with one another, or any other suitable variation ofthe configuration described above. Note that the size of width 416 istypically small relative to the distance between ends 404 and 406 (e.g.,about 15 mm), so that markers 408 will not overlap with the ink imageformed on the surface of substrate 402.

As described in FIG. 2A above, markers 408 may be formed by engravingthe multilayered structure of blanket 400, but may additionally oralternatively be formed using other suitable processing techniques, suchas by ink-jetting, by three-dimensional (3D) printing, by applyingmagnetic materials between the layers and/or on top of an outer layer ofthe blanket.

FIG. 4B is a schematic top view of a blanket 410, in accordance with anembodiment of the present invention. Blanket 410 may replace, forexample, blanket 210 of system 11. In some embodiments, blanket 410comprises two linear encoders 411 and 413, formed, respectively,adjacent to ends 404 and 406 of blanket 410, also referred to herein asthe bevels of substrate 402. Encoder 411 comprises a plurality ofmarkers 418 interleaved with and separated by respective buffers 422,such that every pair of a marker 418 coupled to a respective buffer 422forms a marker pitch 424. Similarly, encoder 413 comprises markers 428interleaved with and separated by respective buffers 432, such that apair of a marker 428 coupled to a respective buffer 432 form a markerpitch 434.

In the example of FIG. 4B, encoders 411 and 413 are substantiallyidentical to one another, and are formed at substantially identicaldistances from ends 404 and 406, respectively. Similar to encoder 401 ofblanket 400, encoders 411 and 413 are integral parts of blanket 410, andare typically formed during the production process of blanket 410.

FIG. 4C is a schematic top view of a blanket 420, in accordance, with anembodiment of the present invention. Blanket 420 may replace, forexample, blanket 210 of system 11. In some embodiments, blanket 420comprises two different linear encoders 421 and 423, formed,respectively, adjacent to ends 404 and 406 of blanket 420. Encoder 421comprises a plurality of substantially identical markers 438 having awidth 446 and are interleaved with and separated by respective buffers442, such that a marker pitch 444 comprises a pair of marker 438 andbuffer 442 coupled to one another. Similarly, encoder 423 comprisesmarkers 448 having a width 456 and are interleaved with and separated byrespective buffers 452, such that a marker pitch 454 comprises a pair ofmarker 448 buffer 452 coupled to one another.

In the example of FIG. 4C, encoders 421 and 423 differ from one another,for example width 446 is larger than width 456, and pitch 444 is largerthan pitch 454. Furthermore, encoders 421 and 423 may be formed atsubstantially identical distances from ends 404 and 406, respectively,or at different distances. Encoders 421 and 423 are integral parts ofblanket 420, and are typically formed during the production process ofblanket 420 using one or more of the production techniques describedabove.

The configurations of blankets 400, 410 and 420 are provided purely byway of example for the sake of clarity of the present invention. Inother embodiments, an encoder, such as encoder 401 may comprise anysuitable type of markers, such as a grid marker, a motion encoding code,a one-dimensional (1D) barcode, a two-dimensional (2D) barcode, and athree-dimensional (3D) barcode. Furthermore, each of the 2D barcodes maycomprise a quick response (QR) code, an AZTEC code, and/or any othertype of a 2D barcode.

Additionally or alternatively, the 3D barcodes may be produced byengraving a 3D structure (e.g., a trench, a hole, or a staircase) one ormore of the blanket layers, and/or by producing a 3D structure thatforms a topographic outer surface of the blanket (e.g., forming a 3Dstructure between the layers, thereby forming topography on the outersurface of the blanket,) and/or by producing a 3D structure within theengraved 3D structure (e.g., triangles 334 of FIG. 3A above). Asdescribed above, the 3D structures may be formed between the blanketlayers, as part of at least one of the outer layers, or disposed on theupper surface of the outer layer of the blanket.

Moreover, the 3D structures may be formed using 3D printing or any othersuitable techniques during the production of the blanket. Note that theuppermost surface of the 3D structure may be within the engravedstructure (e.g., between the blanket layers), or flush with the surfaceof the outer layer of the blanket, or extends out of the surface of theouter layer of the blanket.

Similarly, the 1D and 2D barcodes may be formed using at least one ofthe above techniques applied for producing the 3D structures. Forexample, by engraving 1D or 2D structure in the blanket and filling theengraved structure with a filling material such that an outer surface ofthe filling material is flush with the outer surface of the outer ayerof the blanket.

In other embodiments, the markers may be formed by engraving structuresat predefined locations in the outer surface of the outer layer of theblanket, and jetting ink droplets adapted to adhere only to the surfaceof the engraved structures. Additionally or alternatively, the markersmay be produced by jetting ink droplets between the blanket layersand/or on top of the outer layer of the blanket.

As described in FIG. 2C above, the blanket (e.g., blanket 420) isconfigured to stretch during the operation of system 11.

In some embodiments, the encoders (e.g., encoders 421 and 423) areintegrated into blanket 420, and therefore, are configured to indicatean amount of stretching of blanket 420. In the example of FIG. 4C, whenblanket 420 expands, e.g., by one percent, at least one of markers 438and 448 and at least one of respective buffers 422 and 452, may expandby one percent or by another amount indicative of the stretching amountof blanket 420.

In some embodiments, processor 20 is configured to receive from thesensing assemblies, signals indicative of the stretching amount ofmarkers 438 and 448 and buffers 422 and 452 and, based on the signals,to estimate the amount of stretching of blanket 420. Based on theestimated amount of stretching, processor 20 may adjust variousparameters of the printing process so as to compensate for thestretching of blanket 420.

FIG. 4D is a schematic top view of a blanket 430, in accordance withanother embodiment of the present invention. Blanket 430 may replace,for example, blanket 210 of system 11. In some embodiments, blanket 430comprises guiding elements arranged along a longitudinal axis 291 ofblanket 430. In the example of FIG. 4D, the guiding elements comprisetwo parts (typically halves) of zippers, referred to herein as zipfasteners 433, which are coupled to the longitudinal edges of blanket430, such as ends 404 and 406 described above. In other embodiments,only one of zip fasteners 433 is engaged with a respective longitudinaledge of blanket 430. In alternative embodiments, blanket 430 maycomprise any other suitable type of guiding elements.

In some embodiments, zip fasteners 433 are configured to engage, alonglongitudinal axis 291, with a guiding subsystem of system 10, so as tomove blanket 430 along the movement axis represented by arrow 290. Insome embodiments, the guiding subsystem may comprise, inter-alia, theaforementioned rollers (e.g., rollers 232, 240, 242 and 253) describedin FIG. 1 above, and guiding tracks 435, which are configured to engagewith blanket 430 as will be described in detail below.

In an example embodiment shown in FIG. 4D, one zip fastener 433 isengaged with a respective guiding track 435 of the guiding subsystem.This configuration is shown for conceptual clarity and for a detaileddescription of zip fastener 433 depicted below. In another embodiment,the guiding subsystem of system 10 may comprise two guiding tracks 435positioned at both sides of blanket 430. In an embodiment, both zipfasteners 433 of blanket 430 are engaged with both respective guidingtracks 435, along a continuous path parallel to longitudinal axis 291.

In some embodiments, the engagement between zip fasteners 433 andguiding tracks 435 enables the guiding subsystem to apply lateraltension to blanket 430, so as to maintain substrate 402 taut along Yaxis. The engagement also enables the guiding subsystem to applylongitudinal force to substrate 402, so as to rotate blanket 430 alongthe continuous path, in the direction of the movement axis representedby arrow 290.

In some embodiments, zip fasteners 433 comprise strips 465, which can bemade from substantially identical or different materials, and sewn orotherwise coupled, to at least one of ends 404 and 406.

In some embodiments, the guiding subsystem may comprise different typesof guiding elements, for example, strips 465 may have mutually differentgrades of elasticity. Examples of zip fasteners suitable for use withvarious types of ITMs, in system 10 and in other configurations ofprinting systems, are described in detail, for example, in PCT PatentApplication Publication WO 2013/136220 and in PCT Patent ApplicationPCT/IB2018/058009, whose disclosures are all incorporated herein byreference.

In some embodiments, zip fastener 433 comprises a plurality of similaror different lateral formations formed along the longitudinal edge ofstrips 465, in the present example, the lateral formations compriseteeth 458 having a width 466 of about 1 cm or any other suitable sizeand a length 468 of about 5.5 mm or any other suitable size. Teeth 458are interleaved with and separated by respective predefined spacing,referred to herein as buffers 462. In this configuration, zip fastener433 comprises a marker pitch 464 of about 7.5 mm or any other suitablesize, which comprises a pair of one tooth 458 and one buffer 462.

In an embodiment, zip fastener 433 may comprise any suitable number ofteeth 458, such as but not limited to between 3000 and 8200 teeth. Inthis embodiment, length 468 of a single tooth 458 may be between 0.003%and 0.005% of the total length of blanket 430. In another embodiment,each zip fastener 433 may comprise more than 500 teeth 458, for example,about 1375 teeth 458, so that in case of two zip fasteners 433 coupled,respectively, to ends 404 and 406, blanket 430 may comprise a totalnumber of about 2750 teeth 458. In this embodiment, length 468 of asingle tooth 458 may be about 0.05% of the total length of blanket 430.In these embodiments, length 468 of a single tooth 458, also referred toherein as a longitudinal marker dimension, may be between 0.003% and0.05% of the total length of blanket 430, also referred to herein as alongitudinal ITM dimension.

In some embodiments, guiding track 435 of the guiding subsystemcomprises teeth 459 (or any other suitable type of lateral formations)positioned, along longitudinal axis 291, at a predefined spacing fromone another. In some embodiments, teeth 459 and 458 have size, shape andarrangement that enables the aforementioned engagement between zipfastener 433 and the respective guiding track 435.

In some embodiments, at least one of zip fasteners 433 may act as alinear encoder having markers, such as teeth 458, buffers 462, markerpitch 464, or any suitable combination thereof.

In some embodiments, system 11 comprises sensing assemblies, such assensing assemblies 55A-55H of FIG. 1 above. The sensing assemblies areconfigured to produce, in response to sensing at least one of themarkers of zip fasteners 433, electrical signals, such as positionsignals indicative of respective positions of the respective markers.

As described above, based on the position signals received from sensingassemblies 55A-55H, processor 20 is configured to control the torqueapplied to blanket 430 by each roller, so as to maintain the upper runof blanket 430 taut and isolated from being affected by the mechanicalvibrations at the lower run.

In some embodiments, in response to a stretching of substrate 402, theaforementioned markers of zip fastener 433 are configured to indicate anamount of stretching of blanket 430. For example, the size of one ormore buffers 462, and marker pitches 464 may increase.

In some embodiments, teeth 458 may be shaped to improve the accuracy ofthe position signals received from sensing assemblies 55A-55H. Forexample, teeth 458 may have at least one sharp edge that may be sensedby sensing assemblies 55A-55H with high repeatability. For example, oneor more of teeth 458 may have any suitable geometrical shape, such asbut not limited to, a round shape, a rectangular shape, a square shape,a trapezoid shape, or a star shape.

In some embodiments, one or more markers of zip fastener 433, e.g.,teeth 458 or buffer 462, may have a protrusion and/or an intrusion thatmay improve the sensing repeatability of sensing assemblies 55A-55H.

In other embodiments, one or more teeth 458 or any other markers of zipfastener 433, may comprise magnetic material, which may be sensed by oneor more suitable magnetic sensing assemblies mounted on system 11.

Additionally or alternatively, at least some markers of zip fastener 433(e.g., teeth 458 or buffer 462) may have two or more colors having adistinctive divider that may further improve the sensing repeatabilityof sensing assemblies 55A-55H.

In alternative embodiments, each zip fastener 433 may have a differentconfiguration of markers, such that blanket 430 may comprise twodifferent encoders in close proximity to ends 404 and 406, as describedfor example in blanket 420 of FIG. 4C above.

In some embodiments, processor 20 may use the two different encoders forproducing two respective sets of position signals. The differentposition signals may be used for controlling two different aspects inthe process of applying the ink image to the surface of substrate 402.

In some embodiments, the sets of markers may differ from one another,for example, in width or buffer size, or pitch or a combination thereof.

In some embodiments, at least one of the markers of zip fastener 433 maycomprise at least one code, such as the grid marker or motion encodingcode described in FIG. 3C above.

In other embodiments, at least one of the markers of zip fastener 433may comprise a one-dimensional (1D) barcode, a two-dimensional (2D)barcode, or a three-dimensional (3D) barcode. For example, at least someteeth 458, or buffers 462, or a combination thereof, may have one of theaforementioned barcode patterned or engraved, or printed thereon.

The configuration of zip fastener 433 is shown by way of example, inorder to illustrate motion control problems that are addressed byembodiments of the present invention and to demonstrate the applicationof these embodiments in enhancing the printing performance of system 11.Embodiments of the present invention, however, are by no means limitedto this specific sort of example encoder, and the principles describedherein may similarly be applied to other sorts of substrates andtransfer members used in any other sorts of printing systems.

FIG. 5A is a schematic sectional view of a blanket 500, in accordancewith an embodiment of the present invention. Blanket 500 may replace,for example, blanket 210 of system 11. In some embodiments, blanket 500comprises multiple 3D structures 504 (e.g., trenches or holes described,for example, in FIG. 4C above) engraved in one or more layers of asubstrate 502 having a thickness 531.

In an example embodiment of FIG. SA, all structures 504 havesubstantially identical width 508 and depth 515, and are separated byrespective buffers 514. Moreover, structures 504 have a symmetricalsectional shape with sidewalls 506 substantially orthogonal relative toa top surface 516 and to a bottom surface 511. Note that adept-to-thickness ratio, e.g., between depth 515 and thickness 531, mayhave any value between 0.01 and 0.99.

As depicted in FIG. 4C above, after engraving, structure 504 may be atleast partially filled with any suitable filling material, also referredto herein as a filler layer (not shown in FIG. 5A).

In another embodiment, the depth-to-thickness ratio may differ betweenstructures. For example, at least two 3D structures may have differentlevels of depth 515. Furthermore, in the example of FIG. 5A, surface 511is substantially parallel to top and bottom surfaces 516 and 510,respectively. In alternative embodiments, surface 511 may not beparallel to any of surfaces 516 and 510, e.g., inclined at one side,resulting in different lengths between sidewalls 506.

FIG. 5B is a schematic sectional view of a blanket 520, in accordancewith an embodiment of the present invention. Blanket 520 may replace,for example, blanket 210 of system 11. In some embodiments, blanket 520comprises multiple 3D structures 524 (e.g., trenches or holes described,for example, in FIG. 4C above) engraved in one or more layers of asubstrate 522 having a buffer 534 separating therebetween and a uniformdepth 525.

In an example embodiment of FIG. 5B, at least two structures 524 haveslanted sidewalls 526 having non-right angles between sidewalls 526 andat least one of top and bottom surfaces 536 and 521, respectively. As aresult, a width 528 between sidewalls 526 measured on surface 521 issmaller than a width 530 measured between sidewalls 526 at the level oftop surface 536.

In alternative embodiments, blanket 520 may comprise a non-uniform depth525 among different structures 524, and/or at least one inclined surfaceamong surfaces 536, 521 and 533, and/or any other variation in thestructure of blanket 520. The variations may be intended by design, orundesired due to variations in the production process of blanket 520.

Note that the two sets of width (e.g., widths 528 and 530) may be usedby sensing assemblies (e.g., assemblies 55A-5514 of FIG. 1 above) forproducing two respective sets of position signals, which may be used forcontrolling two different aspects in the ink image placement processcarried out by system 11. For example, the two sets of position signalsmay be indicative of stress and/or strain between surfaces 533 and 536of blanket 520.

FIG. 5C is a schematic sectional view of a blanket 540, in accordancewith an embodiment of the present invention, blanket 540 may replace,for example, blanket 210 of system 11. In some embodiments, blanket 540comprises a plurality of at least two different 3D structures 543 and544 (e.g., trenches or holes described, for example, in FIG. 4C above)interleaved with one another and engraved in one or more layers of asubstrate 542 having a buffer 554 separating therebetween. Note thatblanket 540 has two sets of structures 543 and 544, interleaved with oneanother such that every structure 543 has two neighbor structures 544and vice versa.

In an example embodiment of FIG. 5C, structures 543 and 544 have auniform depth 545, but their sidewalls are different. Sidewalls 546 ofstructure 543 are substantially orthogonal to at least one of surfaces521 and 536 (similar to sidewalls 506 of blanket 500 depicted in FIG. 5Aabove), whereas sidewalls 558 of structure 544 are slanted and are notorthogonal to at least one of surfaces 521 and 536 (similar to sidewalls526 of blanket 520 depicted in FIG. 5B above).

In some embodiments, the configuration of blanket 540 may enableincorporation of two or more encoders interleaved with one another orarranged at any other suitable configuration. For example, structure 543has substantially identical width 548 between sidewalls 546 at bothsurfaces 556 and 541, whereas structure 544 may have a similar width 548at surface 541 but a typically larger width 550 at the level of surface556.

In some embodiments, processor 20 of system 11 is configured to receivefrom sensing assemblies (e.g., assembly 360 of FIG. 3B above), one ormore sets of position signals produced from structures 543 and 544. Forexample, first and second sets comprising different reflections sensedfrom surface 556 of structures 543 and 544 respectively, and a third setcomprising a double density of reflections sensed from surface 541 ofboth structures 543 and 544. The example configuration of blanket 540provides a user with multiple codes received from one or more sensingassemblies mounted adjacent to blanket 540. Each code may address adifferent aspect related to the control of the ink image placement onsurface 556 (or another top surface shown, for example, in FIG. 7 below)of blanket 540.

Methods for Producing Encoders Integrated in Blankets

FIG. 6 is a diagram that schematically illustrates a sectional view of aprocess sequence for producing a blanket 600 comprising integratedmarkers 612, in accordance with an embodiment of the present invention.Blanket 600 may replace, for example, blanket 210 of system 11.

The process begins at a step 1 withpreparing on a carrier 616, anexemplary stack of five layers comprising blanket 600.

In some embodiments, carrier 616 may be formed of a flexible foil, suchas a flexible foil mainly consisting of, or comprising, aluminum,nickel, and/or chromium. In an embodiment, the foil comprises a sheet ofaluminized polyethylene terephthalate (PET), also referred to herein asa polyester, e.g., PET coated with fumed aluminum metal.

In some embodiments, carrier 616 may be formed of an antistaticpolymeric film, for example, a polyester film. The properties of theantistatic film may be obtained using various techniques, such asaddition of various additives, e.g., an ammonium salt,to the polymericcomposition.

In some embodiments, carrier 616 has a polished flat surface (not shown)having a roughness (Ra) on an order of 50 nm or less, also referred toherein as a carrier contact surface.

In some embodiments, a fluid first curable composition (not shown) isprovided and a release layer 602 is formed therefrom on the carriercontact surface. In some embodiments, release layer 602 comprises an inkreception surface 603 configured to receive the ink image, e.g., fromimage forming station 212 of system 11, and to transfer the ink image toa target substrate, such as sheet 226, shown and described in FIG. 1above. Note that layer 602, and particularly surface 603 are configuredto have low release force to the ink image, measured by a wetting angle,also referred to herein as a receding contact angle (RCA), betweensurface 603 and the ink image, as will be described below.

The low release force enables complete transfer of the ink image fromsurface 603 to sheet 226. In some embodiments, release layer 602 is madefrom a typically transparent silicon elastomer, such as avinyl-terminated polydimethylsiloxane (PDMS), or from any other suitabletype of a silicone polymer, and may have a typical thickness of 50 μm,or any other suitable thickness larger than 10 μm.

In some embodiments, the fluid first curable material comprises avinyl-functional silicone polymer, e.g., a vinyl-silicone polymercomprising at least one lateral vinyl group in addition to the terminalvinyl groups, for example, a vinyl-functional polydimethyl siloxane.

In some embodiments, the fluid first curable material may comprise avinyl-terminated polydimethylsiloxane, a vinyl-functionalpolydimethylsiloxane comprising at least one lateral vinyl group on thepolysiloxane chain in addition to the terminal vinyl groups, acrosslinker, and an addition-cure catalyst, and optionally furthercomprises a cure retardant.

In the example of FIG. 6, release layer 602 may be uniformly applied toPET-based carrier 616, leveled to a thickness of 5-200 μm, and cured forapproximately 2-10 minutes at 120-130° C. Note that the hydrophobicityof ink transfer surface 603 may have a RCA of about 60°, with a 0.5-5microliter (μl) droplet of distilled water. In some embodiments, asurface 605 of release layer 602 may have a RCA that is significantlyhigher, typically around 90°.

In some embodiments, PET carriers used to produce ink-transfer surface603 may have a typical RCA of 40° or less. All contact anglemeasurements were carried out using a Contact Angle analyzer “Easy Drop”FM40Mk2 produced by Krüss™ Gmbh, Borsteler Chaussee 85, 22453 Hamburg,Germany and/or using a Dataphysics OCA15 Pro, produced by Particle andSurface Sciences Pty. Ltd., Gosford, NSW, Australia.

In some embodiments, release layer 602 may have a low release force toseveral types of materials, and therefore layer 602 may not be appliedto locations designated for markers, such as at the bevels of substrate402 described in FIGS. 4A, 4B and 4C above. Further details on theseembodiments are described below.

In some embodiments, blanket 600 comprises a compliance layer 604, alsoreferred to herein as a conformal layer, typically made from PDMS with ablack pigment additive. Compliance layer 604 is applied to release layer602 and may have a typical thickness of 150 pin or any other suitablethickness equal to or larger than 100 nm. Note that compliance layer 604is configured to attenuate substantial intensity of light at selectedwavelengths from being transmitted therethrough and/or from beingreflected therefrom.

It will be understood that the level of attenuation depends on variousparameters, such as layer thickness and wavelength of the light emittedby the sensing assembly. For example, UV wavelengths (10 nm-400 nm) mayhave larger attenuation compared to visible light (400 nm-700 nm) and IR(700 nm-1 mm).

In some embodiments, compliance layer 604 may have mechanical propertiesgreater resistance to tension) that differ from release layer 602. Suchdesired differences in properties may be obtained, e.g., by utilizing adifferent composition with respect to release layer 602, by varying theproportions between the ingredients used to prepare the formulation ofrelease layer 602, and/or by the addition of further ingredients to suchformulation, and/or by the selection of different curing conditions. Forexample, adding filler particles may increase the mechanical strength ofcompliance layer 604 relative to release layer 602.

In some embodiments, compliance layer 604 has elastic properties thatallows release layer 602 and surface 603 to follow closely the surfacecontour of a substrate onto which an ink image is impressed (e.g., sheet226). The attachment of compliance layer 602 to the side opposite toink-transfer surface 603 may involve the application of an adhesive orbonding composition in addition to the material of compliance layer 602.

In some embodiments, blanket 600 comprises reinforcement stacked layers,also referred to herein as a support layer 607 or a skeleton of blanket600, which is applied to compliance layer 604 and is described in detailbelow. In some embodiments, support layer 607 is configured to provideblanket 600 with an improved mechanical resistance to deformation ortearing that may be caused by the torque applied to blanket 600 by therollers and dancers. In some embodiments, the skeleton of blanket 600comprises an adhesion layer 606, made from PDMS or any other suitablematerial, which is formed together with a woven fiberglass layer 608. Insome embodiments, layers 606 and 608 may have typical thickness of about150 μm and 112 μm, respectively, or any other suitable thickness, suchthat the thickness of support layer 607 is typically larger than 100 μm.

In other embodiments, the skeleton may be produced using any othersuitable process, e.g., by disposing layer 606 and subsequently couplinglayer 608 thereto and polymerizing, or by using any other processsequence.

In some embodiments, the polymerization process may be based onhydrosilylation reaction catalyzed by platinum catalyzed, commerciallyknown as “addition cure.”

In other embodiment, the skeleton of blanket 600 may comprise anysuitable fiber reinforcement, in the form of a web or a fabric, toprovide blanket 600 with sufficient structural integrity to withstandstretching when blanket 600 is held in tension in system 11. Theskeleton may be formed by coating the fiber reinforcement with anysuitable resin that is subsequently cured and remains flexible aftercuring.

In an alternative embodiment, support layer 607 may be separatelyformed, such that fibers embedded and/or impregnated within anindependently cured resin. In this embodiment, support layer 607 may beattached to compliance layer 604 via an adhesive layer, optionallyeliminating the need to cure support layer 607 in situ. In thisembodiment, support layer 607, whether formed in situ on compliancelayer 604 or separately, may have a thickness of between about 100micrometers and about 500 μm, part of which is attributed to thethickness of the fibers or the fabric, which thickness generally variesbetween about 50 μm and 300 μm. Note that thickness of support layer 607is not limited to the above values.

In some embodiments, blanket 600 comprises a high-friction layer 610,also referred to herein as a grip layer, made from a typicallytransparent PDMS and configured to make physical contact between blanket600 and the rollers and dancers of system 11 described in FIG. 1 above.Note that although layer 610 is made from relatively soft materials, thesurface facing the rollers has high friction so that blanket 600 willwithstand the torque applied by the rollers and dancers without sliding.In an example embodiment, layer 610 may have a thickness of 100 μm, butmay alternatively have any other suitable thickness, e.g., between 10 μmand 1 mm.

Additional embodiments that implement step 1 of FIG. 6 are described indetail, for example, in PCT International Publication WO 2017/208144,whose disclosure is incorporated herein by reference.

At a step 2, the process comprises engraving 3D structures (e.g., atrench, a hole, or a staircase), referred to herein as markers 612, inone or more of the layers comprising blanket 600. Note that step 2 showsa sectional view of the bevel of blanket 600, in which markers 612 areformed. As shown in FIGS. 4A, 4B and 4C, the markers are formed at thebevel of the blanket so that the markers do not overlap with the inkimage formed on the upper surface of the blanket, Thus, it will beunderstood that the sectional views of FIGS. 6 and 7 represent regionsof the blanket separated from the ink image.

In the example of step 2, markers 612 are formed in layers 602 and 604and may optionally be engraved at least through layer 602, andoptionally also through layer 604, and may be further extended into atleast part of layer 606. In some embodiments, markers 612 are engravedto a depth larger than 200 μm using laser techniques, such as lasermarking or laser ablation. In other embodiments, at least one of markers612 may be engraved into at least part of one or more of layers 602, 604and 606. For example, a first group of one or more markers 612 may beengraved into part of or the entire thickness of layer 602, a secondgroup of one or more markers 612 may be engraved through the entirethickness of layer 602 and into part of or the entire thickness of layer604, and a third group of one or more markers 612 may be engravedthrough the entire thickness of layers 602 and 604 and into part of orthe entire thickness of layer 606.

In yet other embodiments, one or more of markers 612 may be engravedinto at least part of at least one layer of the stack comprising layers602, 604 and 606 and one or more other markers 612 may be engraved intoat least part of one or more other layers of the stack. For example, oneor more markers 612 may be engraved into part of or the entire thicknessof layer 602, and one or more other markers 612 may be engraved intopart of or the entire thickness of layer 604 and/or 606 using anysuitable engraving process described herein.

In other embodiments, markers 612 may be engraved using any othersuitable process, such as DPM using punching or pinning techniques, asdescribed in FIG. 2A above, or by applying any other suitable processingtechnique.

In some embodiments, marker 612 may have a square shape, such as markers408 shown in FIG. 4A, a rectangle shape, such as markers 418 and 438shown in FIGS. 4B and 4C, respectively. Additionally or alternatively,other suitable shapes such as round, ellipse, star, can also be used.Several example shapes are described in FIGS. 4A, 4B and 4C above.

In some embodiments, marker 612 may have any suitable shape in asectional view, such as 3D structure 504 of blanket 500 depicted in FIG.5A above and having right-angle sidewalls 506, or structures 524 ofblanket 520 depicted in FIG. 5A above and having slanted sidewalls 526,or a combination thereof shown, for example, in FIG. 5C, or any othersuitable shape described, for example, in FIGS. 5A, 5B and 5C above.

At a step 3, the process comprises applying a filling material, alsoreferred to herein as a filler layer 614, into the engraved 3Dstructures of markers 612. As described above, release layer 602 mayhave a low releasing force to several types of materials, such as tofiller layer 614, which is configured to fill the engraved 3D structuresof markers 612.

Note that filler layer 614 is configured to adhere to layer 604 and toother lavers of blanket 600 but not to layer 602. In some embodiments,layer 602 may not be applied to locations designated for markers 612,such as at the bevels of blanket 600 as described at step 1 above, andin more details in FIGS. 4A and 4C above. In other embodiments, layer602 may be applied across blanket 600 at step 1, and removed from thebevels of blanket 600 before applying layer 614 at step 3.

In some embodiments, filler layer 614 is configured to have chemicalaffinity to a silicone polymer so as to conform to PDMS-based layers602, 604 and 606. Additionally or alternatively, layer 614 may have anysuitable elastic modulus so as to maintain the flexibility of blanket600.

In some embodiments, filler layer 614 is configured to have mechanicaland chemical stability, at a temperature range between 0° C. and 180°C., in other words, the chemical and mechanical properties of fillerlayer 614 are retained as they are in room temperature, and chemicalresistance, e.g., no thermal decomposition, no weight loss or propertiesloss, are occurred.

In some embodiments, layer 614 is configured to have durability toabrasion and resistance to scratch (e.g., surface hardness larger than30 Shore A) that are comparable to or larger than of blanket 600.Furthermore, layer 614 is configured to receive various types ofadditives so as to control optical attributes, such as transparency,reflectivity and color, magnetic attributes, and resistance tomechanical (e.g., tensile) stress.

The removal of layer 602 from the bevels may be carried out, forexample, by etching at selected locations of the bevels, or by usingother suitable techniques. In other embodiments, layer 602 may beremoved from at least one of the bevels of blanket 600 prior to applyingfiller layer 614 to the respective bevels of blanket 600 comprisingmarkers 612. Step 3 concludes the process sequence of FIG. 6.

The configuration of blanket 600 is provided purely by way of examplefor the sake of clarifying the present invention. In other embodiments,blanket 600 may comprise a single layer or any other suitable number oflayers. In these embodiments, at least one of the layers of blanket 600may comprise any other suitable material such as but not limited to apolytetrafluoroethylene, a polyester, a polyimide, a polyvinylchloride(PVC), a polyolefin, an elastomer, a polystyrene-based polymer, apolyamide-based polymer, a methacrylate-based elastomer, a rubber, apolyurethane, a polycarbonate, an acrylic and a combination of at leasttwo of these materials.

Additionally or alternatively, blanket 600 may comprisethree-dimensional (3D) markers that may be formed by engraving (or usingany other suitable technique) holes and/or trenches in two or morelayers of blanket 600. For example, blanket 600 may comprise an L-shaped3D marker or an inversed T-shaped 3D marker. In such embodiments, thelarge lateral portion of the 3D marker may be formed by engraving, forexample, layer 606, and the smaller portion of the 3D marker (e.g., the“pole” of the “L” or the “leg” of the inversed “T”) may be formed byengraving layer 604. The sensing assemblies described above may sensesuch 3D markers through any transparent or partially transparent layers,so that blanket 600 may comprise an increased density of markers havingany desired shape. Therefore, processor 20 may receive a larger amountand more valuable information on the blanket in question, which mayassist processor 20 in tightening the printing process control andtherefore, may improve the quality of the printed image on the targetsubstrate.

FIG. 7 is a diagram that schematically illustrates a sectional view of aprocess sequence for producing a blanket 700 comprising integratedmarkers 710, in accordance with an embodiment of the present invention.Blanket 700 may replace, for example, blanket 210 of system 11.

In some embodiments, the layers in FIG. 7 are similar to the layers inFIG. 6 above, but undergo different respective process sequences.Therefore, FIG. 7 emphasizes the different sequence of the process.

The process begins at a step 1 with applying a release layer 704 to apolyester (PET) substrate 702, followed by polymerization of releaselayer 704. Subsequently, a compliance layer 706 is applied to releaselayer 704.

In some embodiments, a layer 708 made from any suitable polymer material(e.g. plastic) may be applied to compliance layer 706 so as to protectcompliance layer 706 during the engraving process depicted in step 2below. In other embodiments, step 1 of the process may be concludedafter applying compliance layer 706, without applying layer 708.

At a step 2, the process comprises engraving 3D structures, also refersto herein as markers 710, in one or more layers of blanket 700. Theengraving may be carried out using any of the engraving techniquesdescribed above. In the example embodiment depicted in FIG. 7, the 3Dstructures are engraved through layer 706.

In some embodiments, further to the engraving process, layer 708 isremoved to conclude step 2 of the process. In other embodimentsdescribed in step 1 above, layer 708 is not applied to layer 706. Inthese embodiments, step 2 of the process may comprise an additionalsub-step of cleaning the outer surface of layer 706 and the 3Dstructures of markers 710 from by-product residues of the engravingprocess.

Note that step 2 shows a sectional view of a bevel of blanket 700, inwhich markers 710 are thrilled in regions non-overlapping the ink imageapplied to release layer 704 of blanket 700 during the digital printingprocess.

At a step 3, the process comprises applying a stack comprising a fillingmaterial, also referred to herein as a filler layer 712, which isapplied to a fiberglass layer 714. In some embodiments, filler layer 712is configured to fill the engraved 3D structures of markers 710 and tobe coupled to layer 706. In some embodiments, filling material 712 isconfigured to adhere to the inner part (e.g., the bulk) of release layer704, whereas the outer surface of layer 704 typically exhibits lowadhesion to a wide selection of materials, such as to filling material712.

In some embodiments, layers 712 and 714 are applied to both layer 706and markers 710 in a single operation, and subsequently, layer 712 ispolymerized. In alternative embodiments, layers 712 and 714 may bedisposed using any other suitable sequence.

At a step 4, the process comprises applying a grip layer 716 tofiberglass layer 714. In some embodiments, grip layer 716 issubstantially identical to high-friction layer 610 and is configured toenable firm contact between blanket 700 and the rollers and dancers ofsystem 11. Subsequently, substrate 702 may be removed using any suitabletechnique, such as chemical etching.

Although the embodiments described herein mainly address blankets (ITMs)used in digital printing processes on sheets and web, the methods andsystems described herein can also be used in other applications, such asin drum blanket used in indirect printing systems in which the blanketis wrapped around a drum and is not guided by rollers. The methods andsystems described herein can also be used in any printing system usingan ITM, such that the motion of the is precisely controlled.

It will thus be appreciated that the embodiments described above arecited by way of example, and that the present invention is not limitedto what has been particularly shown and described hereinabove. Rather,the scope of the present invention includes both combinations andsub-combinations of the various features described hereinabove, as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description and which arenot disclosed in the prior art. Documents incorporated by reference inthe present patent application are to be considered an integral part ofthe application except that to the extent any terms are defined in theseincorporated documents in a manner that conflicts with the definitionsmade explicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

Detecting and Compensating for Blanket Stretching

FIG. 8 is a schematic sectional view of a position sensing assembly 800,in accordance with another embodiment of the present invention. In someembodiments, system 11 may comprise a blanket 802, which may replace,for example, blanket 210 of FIG. 1 above. As described, for example inFIGS. 2A-2C above, system 11 is configured to move blanket 802, at apredefined and controlled speed, in the moving direction represented byarrow 290.

In some embodiments, position sensing assembly 800 is configured todetect the position of markers, such as markers 804 and 806 that areengraved (or formed using any other suitable technique) in blanket 802at a distance 813 from one another, and to produce signals indicative ofstretching of blanket 802. As will be described in detail below, thedisclosed techniques may obtain, for a given marker, two or moresignals, indicative of two or more respective positions of the givenmarker. These techniques may be applied to multiple markers of themarked blanket, so as to estimate the actual length of distance 813, orin other words, to detect whether blanket 802 has been deformed, e.g.,due to overstretching.

In some embodiments, position sensing assembly 800 comprises a lightsource 816, such as one or more LEDs, one or more lasers or any othersuitable type of light source, such as those described in detail inFIGS. 2A-2C and 3A-3C above. Light source 816 is configured to emit anddirect multiple light beams, such as light beams 815 and 817, which maypass through markers 804 and 806 of blanket 802. Note that light beams815 and 817 are typically identical to one another.

In some embodiments, position sensing assembly 800 comprises a slitassembly 808 having two or more slits 810 and 812, which are located ata distance 811 from one another and are adapted to respectively passlight beams 815 and 817 that have passed through markers 804 and 806 asdescribed above. In some embodiments, distance 811 between slits 810 and812 is smaller than distance 813 between markers 804 and 806, alsoreferred to herein as an inter-marker distance. In some embodiments,slit assembly 808 comprises a shield 814, which is configured to blockstray light or light scattered between slits 810 and 812. In otherwords, shield 814 is configured to isolate between light beams 815 and817, so that each of light beams 815 and 817 is conveyed throughposition sensing assembly 800 in two separate channels, as will bedescribed below.

In some embodiments, position sensing assembly 800 comprises a fiberassembly 818 having a bundle of multiple optical fibers 820 laid outbetween a lower surface 821 and an upper surface 823 of fiber assembly818. In some embodiments, surfaces 821 and 823 are transparent to lightbeams 815 and 817, and optical fibers 820 are configured to convey lightbeams 815 and 817 through fiber assembly 818.

In some embodiments, position sensing assembly 800 comprises a sensor822, such as but not limited to sensors 271 or 284 described in FIGS.2A-2C above. Additionally or alternatively, sensor 822 may comprise asuitable type of a photodiode or any other suitable sensing apparatus,which is configured to sense light beams 815 and 817, and to produceelectrical signals indicative of the intensity of the sensed lightbeams.

In the example embodiment of FIG. 8, system 11 moves blanket 802 at apredefined speed in the moving direction represented by arrow 290, andlight source 816 emits light beams 815 and 817. When marker 804 isaligned with slit 810, light beam 815 passes through marker 804 andthough slit 810 and fiber assembly 818, and is sensed by sensor 822,which outputs electrical signal 824, also referred to herein as a firstsignal, indicative of the sensed intensity of light beam 815 and of thefirst position of marker 804. Subsequently, system 11 keeps movingblanket 802 at the predefined speed in the direction of arrow 290. Whenmarker 804 is aligned with slit 812, light beam 817 passes throughmarker 804 and though slit 812 and fiber assembly 818, and is sensed bysensor 822, which outputs electrical signal 826, also referred to hereinas a second signal, indicative of the sensed intensity of light beam 817and of the second position of marker 804.

Note that in the example configuration of FIG. 8, position sensingassembly 800 is configured to produce two signals indicative of tworespective positions of a single marker (e.g., marker 804). In otherembodiments, similar techniques may be implemented, mutatis mutandis, inother configurations, such that position sensing assembly 800 may beadapted to obtain any other suitable number of signals from a singlemarker.

In some embodiments, processor 20 receives electrical signals 824 and826 and is configured to estimate, based on the predefined moving speedof blanket 802 and electrical signals 824 and 826, a distance 827, whichis indicative of the distance marker 804 travelled between slits 810 and812. Processor 20 is further configured to compare between estimateddistance 827 and predefined distance 811 (between slits 810 and 812), soas to detect whether or not blanket 802 is deformed, e.g., due tostretching. For example, equal value of distances 811 and 827 mayindicate that blanket 802 is not deformed or stretched, but whencalculated distance 827 is larger than predefined distance 811,processor 20 is configured to alert that blanket 802 has been deformeddue to excess tensile stress by system 11, or due to blanket aging orfor any other reason.

In some embodiments, processor 20 may hold one or more thresholds forcontrolling and compensating for the stretching of blanket 802. Forexample, when distance 827 is larger than distance 811 by a value of afirst threshold, processor 20 may display an alert of stretched blanketon display 34, moreover, processor 20 may adjust the moving speed ofblanket 802, or other process parameters of system 11, so as tocompensate for the blanket stretching. When distance 827 is larger thandistance 811 by a second, larger threshold, processor may display amessage to stop the operation of system 11 and/or may carry out anyother suitable operation so as to compensate for the excess stretchingof blanket 802.

This particular configuration of position sensing assembly 800 andmarked blanket 802 are shown by way of example, in order to illustratecertain problems, such as blanket stretching, which are addressed byembodiments of the present invention and to demonstrate the applicationof these embodiments in enhancing the performance of a digital printingsystem, such as system 11. Embodiments of the present invention,however, are by no means limited to this specific sort of examplesystem, and the principles described herein may similarly be applied toother sorts of position sensing assemblies and/or blankets and/orprinting systems.

The invention claimed is:
 1. A system, comprising: a flexibleintermediate transfer member (ITM) comprising a stack of multiple layersand having one or more markers engraved in at least one of the layers,at one or more respective marking locations along the ITM, wherein theITM is configured to receive ink droplets from an ink supply system toform an ink image thereon, and to transfer the ink image to a targetsubstrate; one or more sensing assemblies disposed at one or morerespective predefined locations relative to the ITM, and configured toproduce signals indicative of respective positions of the markers; oneor more light sources associated respectively with at least one of thesensing assemblies, such that each light source is facing the respectivesensing assembly or coupled to the respective sensor, wherein each ofthe light sources is configured to illuminate the ITM; a slit assembly,which is disposed between the ITM and the sensing assembly and havingfirst and second slits, which are formed at a predefined distance fromone another and are configured to pass, through the slit assembly, oneor more light beams emitted from the light source, wherein, when a givenmarker of the markers is aligned with the first slit, the sensingassembly is configured to produce a first signal indicative of aposition of the given marker aligned with the first slit, and when thegiven marker is aligned with the second slit, the sensing assembly isconfigured to produce a second signal indicative of the position of thegiven marker aligned with the second slit; and a processor, which isconfigured to receive the signals, and, based on the signals, to controla deposition of the ink droplets on the ITM, and wherein the processoris configured to detect a deformation of the ITM based on the first andsecond signals.
 2. The system according to claim 1, wherein at least oneof the markers comprises at least one code selected from a listconsisting of: a grid marker, a motion encoding code, a one-dimensional(1D) barcode, a two-dimensional (2D) barcode, and a three-dimensional(3D) barcode.
 3. The system according to claim 1, wherein when the ITMmoves at a predefined speed relative to the first and second slits, theprocessor is configured to detect the deformation of the ITM, based onthe predefined speed and the first and second signals.
 4. The systemaccording to claim 1, further comprising at least one station orassembly, wherein the processor is configured, based on the signals, tocontrol an operation of the at least one station or assembly of thesystem.
 5. The system according to claim 4, wherein the at least onestation or assembly is selected from a list consisting of (a) an imageforming station, (b) an impression station, (c) an ITM guiding system,(d) one or more drying assemblies, (e) an ITM treatment station, and (f)an image quality control station.
 6. The system according to claim 5,wherein the impression station comprises a rotatable impression cylinderand a rotatable pressure cylinder, configured to transfer the ink imageto the target substrate, and wherein the processor is configured, basedon the signals, to control at least one operation selected from a listconsisting of (a) timing of engagement and disengagement between theimpression and pressure cylinders, (b) a motion profile of at least oneof the impression and pressure cylinders, and (c) a size of a gapbetween the disengaged impression and pressure cylinders.
 7. The systemaccording to claim 5, wherein the processor is configured to control,based on the signals, at least one of: (a) a drying process applied byat least one of the drying assemblies for drying the ink dropletsdeposited on the ITM, (b) a velocity of one or more rollers of the ITMguiding system, (c) at least one of a cooling process, a cleaningprocess and a treatment process of the ITM at the ITM treatment station,or (d) at least one imaging parameter of a digital image of the inkimage acquired and processed by the image quality control station. 8.The system according to claim 1, wherein the one or more markerscomprises a continuous marker formed along at least a portion of theITM.
 9. The system according to claim 1, wherein at least one of themarkers engraved in the ITM comprises filling material, which isconfigured to fill at least part of a structure formed in at least oneof the ITM layers.
 10. The system according to claim 9, wherein thefilling material is configured to change at least one optical propertyof at least one of the ITM layers, or to change at least one opticalproperty of the entire ITM.
 11. The system according to claim 1, whereinthe stack of multiple layers comprises at least a first layer and asecond layer, which is disposed on the first layer, and wherein at leastone of the markers is engraved into at least part of at least one of thefirst and second layers.